ES2979979T3 - Method for manufacturing fire retardant materials and related products - Google Patents

Abstract

A method for manufacturing fireproof material including a fireproof cellulosic insulation. The method includes a device for adding fibers of one or more feedstocks and a fireproof chemical to a mixer prior to drying the fibers. The fibers are separated prior to or during mixing with the fireproof chemical. The feedstock may include old newsprint (ONP), old corrugated containers (OCC), and/or other cellulose-based materials. The method further includes retaining the separated fiber feedstock and chemical together for a sufficient time to ensure adhesion and impregnation of a sufficient amount of the chemical to and in the fibers after the drying process. The separated fibers may be split/sorted prior to and/or after treatment. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Method for manufacturing fire retardant materials and related products

Background of the invention

1. Field of the invention

The present invention relates to the manufacture of fire retardant materials. More particularly, the present invention relates to the manufacture of a blown-in-place fire retardant insulation. Even more particularly, the present invention relates to a blown-in-place insulation made of cellulosic material treated to be fire retardant.

2. Description of the state of the art

Insulation is widely used for passive thermal control in a wide range of applications, with building insulation being a particularly substantial application. Inorganic glass fiber has been the most common type of material used to produce insulation. Fiberglass insulation is supplied in blanket and blown fiber form, and the thickness, density, and fiber structure of the blanket or blown fiber fill are determinants of the insulation's effectiveness, along with the installation method, which also affects effectiveness.

Concerns beyond the effective in-situ (installed) performance of fiberglass, as well as the limited fire retardant characteristics and environmental characteristics of the product, which are regulated by federal and national toxicological standards, have raised public and governmental concerns about its continued use as a thermal insulation product. Organic cellulose insulation has been considered as a type of alternative to fiberglass, and may be desirable for that purpose, especially for its environmental suitability and thermal efficiency. Some cellulose insulation is made from recycled raw material, with recycled newsprint being the primary raw material. Other types of materials, such as cardboard, construction lumber scraps, and the like, have been considered to increase the volume of raw material available to produce cellulose-based insulation.

Cellulose insulation is manufactured in part by using existing papermaking machinery and methods. Specifically, cellulose feedstock in the form of waste paper, typically in the form of printed newspaper, is ground, chopped, or otherwise mechanically reduced into small pieces. In order to ensure that the cellulose insulation meets the fire retardant standard, the pieces are mixed with a fire retardant chemical, which is usually a chemical in powder (i.e., solid) form. The powder must adhere to the fibers, and existing methods of adhering the chemical powder to the fiber, which may include mechanical impact and/or the use of an oil to improve adhesion, have limited effectiveness. Examples of such fire retardant chemicals include boric acid, borax, ammonium sulfate, monoammonium phosphate, diammonium phosphate, sodium tetraborate, ferrous sulfate, zinc sulfate, magnesium sulfate, and mixtures thereof. The treated pieces may then be fiberized, fluffed or otherwise reduced in size to reduce the overall bulk density of the treated insulation, and improve its suitability for introduction into the structure to be insulated.

The adoption of cellulose insulation as an alternative to fiberglass insulation has been limited for several reasons. First, the cost of manufacturing has limited the applications where it is economically competitive. Second, the conventional recycled material used as raw material is not suitable for producing enough material to meet market demand as a substitute for fiberglass. In addition, the method of converting various types of recycled raw material can significantly affect the cost of processing. Third, the method of bonding the fire retardant material to the cellulose chips requires the use of a considerable amount of the treatment material. In the case of powder treatment material, there are challenges in getting the powder treatment material to adhere to the fibers. An excess of fire retardant material is often used, which can lead to excessive dust during installation as well as increased manufacturing costs. When installers apply the material on a construction site, a portion of the fire retardants become airborne and can become an irritant that can also limit visibility.

Several related products and processes have been described and developed to address perceived limitations in manufacturing a viable cellulosic insulation material. U.S. Patent Nos. 5,534,301 and 6,025,027 to Shutt, and U.S. Patent Nos. 4,386,119 and 4,454,992 to Draganov, describe the use of liquid borate to reduce the amount of borate required to coat cellulose insulation fibers. However, the processes described in those patents involve applying the liquid borate to dry fibers. This method has limited commercial value and may not adequately address the difficulty of bonding the fire retardant chemical to the fibers. In addition, the use of liquid borates can cause fiber embrittlement and breakage, which increases the dustiness of the finished product, and can adversely affect the density and insulation value of the product. More recently, U.S. Patent No. US-9,045,605 describes a process for reducing dust associated with the manufacture of a fire retardant cellulose insulation material, in which cellulose material that has been sprayed with liquid fire retardant chemicals is dried and then screened to make the final product less dusty. In the process, individual fibers are separated from each other in the dry state, resulting in undesirable fracture of relatively brittle fibers and formation of excess dust. In addition, fire retardant chemicals are contained in the residual dust removed from the finished product, and therefore the finished product loses valuable fibers and flame retardants. That process is expensive and less effective in producing a cellulose insulation material with more satisfactory fire retardancy than is available with the present invention.

US-2011/095245 A1 describes a method for manufacturing fire retardant fibers, comprising the steps of introducing a fiber feedstock into a mixing tank, adding a fire retardant chemical to the mixing tank, retaining the fiber feedstock and the chemical in the mixing tank for a period of time sufficient to retain the chemical on the fibers of the fiber feedstock after drying the fibers, drying the fibers of the fiber feedstock to form a chemically treated pulp cake, and fluffing the pulp cake to form the fire retardant fibers.

US-2007/137805 A1 describes a process for recovering organic cellulosic fibers from landfill materials, such as post-consumer, municipal and industrial waste materials, comprising the steps of selectively introducing waste materials containing organic cellulosic fibers into a size reducing machine, transporting said previously cleaned waste material to a tank, drum or tunnel type fiber recovery apparatus, and subjecting said waste material for a selected period of time to mechanical and fluid fiberization.

From US-4,349,413 A a process for preparing a fire-resistant cellulosic thermal insulation suitable for being blown in situ is known. The process consists of the steps of introducing cellulosic material selected from the group consisting of hardwood chips, softwood chips, straw, bagasse and mixtures thereof, into a pressurized chamber, pretreating said cellulosic material with steam under pressure and at an elevated temperature for a period of time sufficient to soften said cellulosic material and hydrate it by steam impregnation. The process further consists of the steps of passing the pretreated material to a fiberization stage utilizing a refiner, and injecting a fire retardant chemical selected from the group consisting of borax, boric acid, a borate and mixtures thereof, into said softened material, at the eye of the refiner immediately prior to the grinding segments, fiberizing under pressure for a period of time sufficient to produce an insulating grade cellulosic pulp, and discharging the fiberized material from the fiberization stage and drying it.

What is needed, therefore, is a method to cost-effectively manufacture a fire-retardant cellulosic insulation. What is also needed is such a method that can be used with new raw materials, instead of, or in addition to, conventional material (including, for example, corrugated cardboard and recycled newsprint). Furthermore, what is needed is a method to improve the method of applying the fire-retardant chemical for retention of the fire-retardant chemical on and in the cellulosic material, and to minimize the inclusion of dust in the final product.

Summary of the invention

The invention is defined by the appended claims. Embodiments of the invention result from the dependent claims and the following description.

An object of the present invention is to provide a method for manufacturing a blown-in-place fire retardant cellulosic insulation in a cost effective manner. What is also needed is such a method that can be used with new raw materials, instead of, or in addition to, conventional material (including, for example, corrugated cardboard and recycled newsprint). Furthermore, what is needed is a method for improving the method of applying the fire retardant chemical for retention of the fire retardant chemical on and in the cellulosic material, and for minimizing the inclusion of dust in the final product.

These and other objects are achieved by the present invention, which is a method for manufacturing a blown-in-place fire retardant cellulosic insulation. The feedstock may be inorganic material, but may also be organic material; organic material may be preferable to avoid the limitations and potential safety concerns associated with inorganic material. The method is suitable for use in manufacturing an insulation product from one or more feedstocks. The one or more feedstocks may include one or more recycled cellulosic feedstocks, one or more virgin pulp feedstocks, one or more agricultural fiber sources, and combinations thereof. The amount and type of recycled material and/or virgin material may be selected. The virgin feedstock may be used to obtain the amount of pulp required to fill insulation orders, depending on the availability of the recycled feedstock. Old newsprint (ONP) may be one type of recycled feedstock. Another suitable type of recycled material feedstock is old corrugated containers (OCC). The invention is not limited to just these two recycled material feedstocks. Additional fiber feedstocks could include agriculturally derived fiber sources such as cereal straw, animal feathers, wood byproducts, and other lignocellulosic agricultural byproducts. The invention may include the use of a single feedstock of any type or any other type, provided that its characteristics are taken into account in the process of combining it with a fire retardant chemical. The feedstock is treated to determine its fire retardancy in a mixer that includes a fluid solvent such as, but is not limited to, water. The ratio of liquid to solids by weight may be selected, and may be as low as 20/80 or as high as 99/1.

A system for combining cellulose feedstock and chemical treatment includes a chemical treatment source with an input component. The chemical treatment source includes a liquid solution or suspension of the treatment material, which may be a combination of a fire retardant chemical, such as a borate or other suitable compound, at least one solvent, such as water, and other optional additives that may be of interest. It should be understood that a number of suitable fire retardant chemicals may be employed to treat the cellulosic material. For example, boric acid, borax, ammonium sulfate, monoammonium phosphate, diammonium phosphate, sodium tetraborate, ferrous sulfate, zinc sulfate, magnesium sulfate, and mixtures thereof are suitable. The chemical treatment materials may be dissolved or suspended in at least one solvent. One aspect of the invention is that the fire retardant chemical is combined with the feedstock in liquid form, rather than in solid form, to provide effective bonding of the fire retardant chemical to the surface and basic structure of the feedstock component. More specifically, the fire retardant may be allowed to diffuse into the outer surface of the fibers of the feedstock and/or diffuse into the core of the fibers.

One or more additional additives may be incorporated into the treatment method. For example, a chemical, biological, or other additive may be used to remove or reduce one or more components of the feedstock that may result in a product with undesirable characteristics. For example, a cellulosic feedstock that is a recycled material may include one or more binding agents comprising polysaccharides, starches, and the like that, if carried over into the final product, may facilitate mold growth. An additive, such as an enzyme or other component, to break down such undesirable components, and/or render them sufficiently fluidized so that they may be removed from the treated feedstock, may be added to the mixing tank as one aspect of the present invention. A biocide may be added to minimize mold growth.

The chemical treatment source is combined with the plurality of fibers at one or more selectable steps of the method of manufacturing the cellulose insulation, prior to final drying of the cellulose material. For example, the input component for the chemical treatment source may be coupled to the mixing tank for introduction of the chemical treatment at that point in the method when the fibers are suspended in a mostly liquid state. However, it should be understood that the input component for the chemical treatment source may be located elsewhere, including other component locations in the system, so long as it is in liquid form when in contact with the cellulose feedstock. Examples of alternative processing steps include applying a fire retardant liquid at the mixing stage (after partial dewatering) and/or spraying dry paper with a fire retardant liquid. Additionally, dry chemical treatment materials (such as powders) can be post-applied to materials being treated with fire retardant liquids, to obtain specific properties or chemicals that can be advantageously applied in a dry state to a wet surface.

The system of the present invention further includes conventional components including, but not limited to, one or more wet separation devices (including wet classifying devices), dewatering devices, one or more water recovery and return devices, optional fiber coloring and/or bleaching devices, one or more dryers, dust collectors, coolers, fluffers, fiberizers, dry classifiers, product collectors, and all necessary conduits to transfer material between the devices of the system. The system may be substantially incorporated into a conventional pulp and fiber production process of the type typically used in the papermaking industry, for example, rather than as a completely separate or extensive adjunct to a conventional process. Examples of devices of the system will be described herein, several of which exist in conventional pulp/paper processing facilities currently in existence.

The system includes a mechanism to separate the fibres from each other prior to treatment with a fire retardant. Conventional pulping and screening systems from the paper processing industry can be used to separate the fibres. The purpose of this stage is to gently break up the woven or formed fibre structures (such as paper) to unwind, uncouple and release the individual fibres. This can occur with the fibre while it is in a suspended state, where a liquid, such as water, is used as a medium to transport the fibre.

The system may also include one or more partitioning devices for separating the material stream into various component streams with different properties. For example, one partitioning device may separate heavy components such as metals and glass from the fiber; another partitioning device may separate longer fibers from shorter fibers. Partitioning devices that separate fiber types from each other will also be referred to herein as classifiers. Cyclonic devices may be used to remove heavy elements from the fiber stream. Fiber screening devices may also, or alternatively, be used to divide the fibers based on fiber size. The partitioning system may include means for removing plastics and other products that may float when the fibers are suspended in a slurry.

The system and related method of the present invention provide an efficient and cost effective way to manufacture a viable blown-in-place cellulose insulation product. The method can be used to manufacture other types of fiber-based products that require treatment to establish desired characteristics. Separating the fibers and splitting and/or sorting the fibers in a wet state prevents fiber breakage as compared to conventional dry processing. The introduction of chemical treatment to the pulp prior to fiber drying results in a reduction in chemical treatment costs and overall insulation processing costs. The system and method offer the option of using only recycled cellulosic material as feedstock, or a combination of such feedstock with other materials, to ensure an adequate and sustainable supply of feedstock. The system and method may also include the introduction of fire retardant chemical treatment prior to a drying step of the manufacturing process. This results in more effective bonding or impregnation of the fire retardant product with the insulation fibres, whilst reducing the amount of treatment to be used to produce effective fire retardancy.

The present invention allows for the manufacture of blown-in-situ fire retardant insulation materials. The raw material used to manufacture the fire retardant insulation material may be of any type, but is not limited to paper, pulp, containers, or other specific form of material. The invention provides for the blending of a fire retardant product with the raw material prior to drying the blend. The fire retardant product may be in liquid form when blended with the raw material. The fire retardant chemical may be blended with the at least one solvent so that it is in liquid form prior to contacting the fibers. The fire retardant chemical may be in dry form and blended with the fibers, then introduced into the at least one solvent so that it is in liquid form. The fire retardant chemical may be in dry form and blended with wet fibers so that the solvent in the fibers effectively dissolves it when it comes into contact with the fibers. The combination of the fire retardant product and the raw material may be further processed to form a web, a sheet, a plurality of fibers, or other suitable form. The combination of raw material and fire retardant may be further processed to make insulation, as indicated, or other end products where fire retardancy is a desirable characteristic.

The present invention separates the fibers from each other while they are wet, prior to fire retardant treatment. By separating the fibers while they are wet, there is less fiber breakage compared to when such separation occurs while the fibers are dry, which has been the process up to the present invention. This reduces dust formation and improves yield. When, optionally, the fibers are split and/or sorted while wet, there is also less fiber breakage compared to when such splitting of the fiber stream is performed while the fibers are dry. This also reduces dust formation.

Fibers that have been separated and/or split in the wet state may be mixed in the wet or wet state with fibers obtained from other sources. For example, fibers from various raw material sources may be mixed together in the wet state or other fibers may be mixed in the dry state. As another example, recycled paper materials may be mixed with agricultural fibers and/or animal feathers. In addition, dust or smaller fiber fragments recovered from other stages of the production process may be mixed with sorted fibers separated from earlier stages of processing. The mixing of various fiber sources and longer and shorter fibers may assist in the formation of desired fiber superstructures that may, optionally, be created later in this process. Such superstructures may represent the agglomeration of fiber pieces that would otherwise be too small to serve as effective insulation. The agglomeration of fiber pieces may also be useful in reducing dust in the final product, in improving the insulation properties of the final product, and/or in favorably impacting the density of the final product.

The fibers are at least partially dewatered prior to being combined with fire retardant chemicals. In this embodiment of the present invention, there is no need for a large volume of recirculating chemical at the pulping stage, and the same pulp material (without fire retardant yet applied) can be diverted to other applications not requiring fire retardancy. For example, the same pulping system can be used to produce both cellulose insulation and linerboard, and a partitioning system is used to separate the two fiber streams. The water from the linerboard system can be recirculated (without fire retardant chemicals), while the fiber stream intended for cellulose insulation is partially dewatered prior to adding chemicals. This eliminates the risks and complexity of recirculating fire retardant chemicals in larger linerboard operations. These advantages are in addition to those known when combining fibers and fire retardant chemicals in liquid form, including reduced chemical requirements and reduced dust generation. Additionally, fire retardant in liquid form is more effective in making the treatment penetrate the fibers.

These and other features and advantages of the present invention will become apparent upon review of the following detailed description, the accompanying drawings, and the appended claims.

Brief description of the drawings

Figure 1 is a simplified block diagram representation of the method steps and system components associated with manufacturing the blown-in-situ cellulose insulation of the present invention. The dashed lines represent functions, components, and optional steps.

Detailed description of embodiments of the invention

While the following description relates to the embodiment of the invention wherein a blown-in-place organic cellulosic insulation is manufactured, it should be understood that the invention is not limited thereto. Rather, the present invention provides a method for cost-effectively producing a blown-in-place cellulose-based insulation having adequate fire retardancy using one or more recycled cellulose-based feedstock materials. Furthermore, the present invention enables the manufacture of such a product while reducing the inclusion of powdered material in the finished product. The steps of the described method may be performed in a different order without departing from the scope of the invention, including, but not limited to, the order in which the components are added to a mixer.

Referring generally to Figure 1, a cellulose insulation of the present invention is created when cellulose-based feedstock material that might otherwise be waste material, herein referred to as recycled feedstock material 10, and/or other feedstock materials is combined or blended with one or more fire retardant chemicals to produce a blown-in-situ fire retardant cellulose insulation product. The one or more feedstock materials are reduced to fiber form prior to, or in conjunction with, blending with the one or more fire retardant compounds in a liquid environment. The recycled feedstock material 10, along with optional virgin feedstock 20 and/or recovered wet fibers 30 are transferred to a fiber generating apparatus, such as a pulper 40, for example. Other means for generating fibers from the feedstock are known to those skilled in the art, and may also include recovering dry fiber streams from downstream processes.

A pulper 40 may be used to separate the fibers from each other. Agitation of the fibers in the presence of a liquid such as water may be an effective means of separating the fibers to some extent. The pulp generated in the pulper 40 may be transferred to a partitioning device 50 to remove contaminants and/or to classify the separated wet fibers prior to introducing the fibers into a mixer 60. The partitioning device 50 may be a wet classification system such as a screening system that separates the fibers by fiber size. The partitioning device 50 may also be a cyclone separator that separates heavy materials from lighter materials. The partitioning device 50 may also have multiple stages and multiple functions, such as combinations of cyclone separators and screening systems, for the purpose of separating fibers desired for one use from fibers desired for a different use and/or separating waste materials.

All of the separated fibers may be transferred to the mixer 60 or a portion may be transferred to the mixer 60 while the remainder is diverted to another application, such as the manufacture of linerboard, for example. The separated fibers are at least partially dewatered in the dewatering apparatus 80 prior to introduction into the mixer 60, and the effluent from the dewatering apparatus 80 is transferred to a recovery tank 90 to return the recovered wet fiber 30 to the pulper 40. The at least partially dewatered separated fibers, or separated fibers that have not been dewatered, are transferred directly to the mixer 60 or, optionally, may be fluffed and/or chopped in the apparatus 100 prior to introduction into the mixer 60. In addition, the fibers may be agitated within the mixer 60 by chopper blades or other mechanical action that may serve to further separate the fibers while they are still damp or wet. The fundamental function of the chopper 100 is to separate the fibers in a wet state so that they do not clump together, but are predominantly separated. While the fibers may have originally been separated in an upstream pulping process, the pressure dewatering process can have the effect of binding the fibers together, and the chopper 100 can be useful in re-separating the fibers from each other. Because the chopper 100 operates on fibers that are still in a wet state, fiber breakage is again minimized. If fiber superstructures are present while the material is being chopped, the chopper 100 can be adjusted to maintain the integrity of a specific scale of superstructures, while separating other larger clumps, for example.

The separated fibers are mixed in mixer 60 with one or more fire retardant chemicals 110 and one or more solvents. The one or more solvents may be water, another liquid, or a combination of water and another liquid. The solvent may be added to mixer 60 or may come with the separated fibers in transfer from any one of pulper 40, partitioning device 50, dewatering apparatus 80, and fluff/chopper apparatus 100. The one or more fire retardant chemicals may be added to mixer 60 before, during, or after introducing the separated fibers to mixer 60. Optionally, one or more additives 120 may be added to mixer 60 before, during, or after introducing the separated fibers to mixer 60. The one or more additives 120 may be used to improve the characteristics of the separated fibers, to improve fire retardant chemical bonding on and within the fibers. For example, the additives may include one or more enzymes suitable for removing residual adhesive from the recycled feedstock 10. One or more bonding agents 130 may also be added to the mixer 60 before, during, or after the separated fibers are introduced into the mixer 60. The one or more bonding agents 130 may be selected to cause the individual fibers to clump together and remain bonded to one another. The bonding agents may be added to the mixer 60 or may be applied in downstream processes and may cause bonding to occur in the mixer 60 or in a downstream phase, such as during drying.

The bonding between fibers can form fiber superstructures with interstices between the fibers that improve the insulating characteristics of the finished product.

The separated fibers, the one or more fire retardant chemicals 110, and any optional additives and/or bonding agents contained in the mixer 60, are mixed for a period of time sufficient for the fire retardant chemicals to be retained on and within the separated fibers, and to allow sufficient bonding of the fibers to occur prior to completion of processing, if the objective is to form fiber superstructures in the mixer 60. The treated fibers exiting the mixer 60 are transferred to a drying apparatus 140 to be dried to a liquid content in the range of about 5% to about 25% by weight. Optionally, the treated fibers may first be pressed in a pressing apparatus 150. The pressing apparatus 150 may have the function of removing water, assisting in forming a plurality of superstructures, or both functions. Optionally, the treated and dried fibers may be fiberized in the fiberizer 170. The treated and dried fibers may be further optionally classified in the dry classifier 180, either directly from the drying apparatus 140 or from the optional fiberizer 170. The purpose of the dry classifier 180 is to ensure that the properties of the finished product meet the desired size, density and/or hydrodynamic diameter characteristics. The dry classifier may provide as outputs both the desired product and nonconforming materials, which may include dust (smaller than desired particles) or larger clumps (heavier than desired materials). Following optional classification, a selected subset of the treated and dried fibers may then be satisfactorily packaged for use as the finished final product 160.

When the optional dry classifier 180 is employed, nonconforming materials, such as small particles 190 and dust, or large, heavy materials 195, can be removed from the treated and dried fibers comprising the desired product and returned to the mixer or another process stage. The dust can be returned for agglomeration when the one or more binding agents 130 are in the mixer 60 and/or the small particles 190 and dust can be returned to one or more other apparatuses for reconstitution as components of the fiber superstructure of the finished final product 160. The small particles 190 and dust may optionally be diverted to an agglomeration apparatus 200, which may be simply a dry mixer, to combine with one or more supplemental binding agents 210 and/or other supplemental fibers 220 to form additional residual fiber superstructures that may be added to the treated and dried fibers as the final product 160.

The recycled feedstock material 10 may be comprised of one or more recyclable materials that are cellulose-based, including, but not limited to, any plant-based material. Additional fiber feedstocks suitable for use in the invention include agriculturally derived fiber sources, such as cereal straw, animal feathers, and other lignocellulosic agricultural byproducts, for example. The virgin feedstock material 20 may be kraft wood or ground wood pulp (stone or thermomechanical). The ratio of the recycled material 10 to the virgin material 20 and/or the wet recovered fibers 30 may be selected when the combination is used. The feedstock material(s) may be added to the partitioning device 50 at a level of 1% to 30% solids by weight.

As indicated, the virgin feedstock material 20 may be hardwood (1.5 mm), softwood (3.5 mm) (kraft process), or ground wood pulp (<1 mm) (includes stone or thermomechanical process), and/or cellulose pulp fibers, which may be derived from a conventional cellulose processing system prior to bleaching, or immediately thereafter if that is of interest. The pulp exiting the last black liquor washer in a kraft process may be used, for example, prior to moving to the bleaching process (20% weight solids). A pump may be used to move the pulped fibers from the pulper 40 to the partitioning device 50. Those skilled in the art will recognize that any type of material transfer mechanism may be used to move material, including, but not limited to, pulped material, from one location to another, for the process of the present invention.

Recycled newsprint pulp may be obtained from a conventional paper recycling process, such as from ONP #8 and #9 sources, for example. The paper may be introduced into the pulper 40. The pulper 40 is a tank having an agitator and a source of solvent, such as water, to pulp the feedstock. The agitation breaks down the cellulosic material into fiber stems. The one or more fire retardants 110 may be supplied to the mixer 60 in liquid form, for example, by dissolving them in a solvent such as water. The fire retardants 110, when combined with fibers in a liquid environment, adhere better to their surface and are absorbed into the structure of the separate fibers, than when dry fire retardant chemicals are used, and when the liquid fire retardant chemicals are simply sprayed onto the feedstock, rather than onto separate fibers. The fire retardant may be in dry or wet form blended with fiber in wet form, or may be dry or wet blended with fiber and the one or more solvents. The one or more fire retardants may be selected from boric acid, borax, ammonium sulfate, monoammonium phosphate, diammonium phosphate, sodium tetraborate, ferrous sulfate, magnesium sulfate, zinc sulfate, and mixtures thereof. An example of a suitable fire retardant chemical composition is described in U.S. Patent No. US-8,043,384.

The chemical saturation, operating temperature, and residence time in the mixer 60 may be selected to ensure that the finished cellulose insulation contains a sufficient amount of fire retardant material adhered to and in the insulation fibers. The one or more additional additives may be used to hydrolyze starch, polysaccharides, or other undesirable materials, for example, as well as one or more biocides, as desired to minimize mold growth in the final product 160. The chemicals, additives, and/or binding agents may be mixed together prior to transfer to the mixer 60, such as with a mixing valve, or they may be transferred separately to the mixer 60.

The dewatering apparatus 80 is selected from any of a variety of existing systems that take a cellulose pulp slurry and remove the water to a desired solids content. Any type of screw press, twin wire press, vacuum filter, plate and frame press, roller press, or centrifugal drum, for example, may be used as the dewatering apparatus 80. The dewatering system 80 may increase the solids content of the slurry containing the treated fibers to, but is not limited to, about 30% or more.

A pump or other type of material transfer mechanism may be used to transfer the dewatering effluent to the reclaimer 90, which separates the fibers from the fluid. This may be accomplished by a flotation, rotary (vacuum filters), or wire (fabric) system that can effectively remove the fluid. The fibers from the reclaimer move to the wet recovered fiber vessel 30. Excess fluid from the reclaimer 90 may be filtered for use in other process components of the system, or may be introduced into a waste treatment process for disposal.

The optional fluffer/chopper 100 is configured to break up a pulp cake of treated fibers or dewatered treated fibers. The fluffer/chopper 100 may consist of two counter-rotating meshed blades with a discharge to the drying system 140. Any number of fluffers may be used to break up the pulp cake. The pulp cake may be broken up prior to the mixer 60 or internally within the mixer 60 by internal mixer blades which may be designed to separate fibers.

The drying system 140 is used to dry the treated fibers to a desired moisture content, which may range from 8 to 25% moisture content (75 to 92% solids), for example, but not limited to. A dryer, such as, but not limited to, a rotary drum dryer or a flash drying system that breaks up and fluffs the pulp during drying, may be advantageous, but other drying systems, such as microwave dryers and conveyor dryers, may also be employed. A conveyor, auger system, or other form of conveying device may be used to transport the dried, chemically treated fibers to a location for cooling. A dryer system's bleed gas/hot air collection system may be employed to take in moist air and recirculate it back through the drying system 140 to capture waste heat before venting it to the atmosphere.

An optional dry fluffer 165 may be used to separate clumps of material that may have formed in the drying process, minimally affecting the basic fiber structure, while retaining the desired fiber superstructures when such superstructures become part of the final product. Alternatively, an optional fiberizer 170 may be used as a more aggressive measure to further refine the dried, treated fibers by further separating and reducing the size of the fibers after the drying process. Such separated fibers and/or fiber superstructures may optionally be further classified by size using the dry classifier 180. The dry fluffer 165 and fiberizer 170 may be mechanical devices with rotating toothed plates in close proximity to one or more sets of static or counter-rotating toothed plates so that when clumps of fibers are conveyed through the device 165/170, they are subjected to shear forces that separate the fibers. The difference between a fluffer and a fiberizer lies in the aggressiveness of their interaction with the materials; a fluffer more gently separates clumps or groups of fibers, and a fiberizer more aggressively impacts the materials with greater shear (and focuses on separating individual fibers). A hammer mill is an example of a fiberizer, but there are also fiberizers formed with one or more rotating toothed plates in close proximity to one or more stationary or counter-rotating toothed plates. Traditional fiberizers used to manufacture cellulose insulation with dry fire retardants mix the chemical and fiber in a high-speed grinding motion, which can have the effect of pressing the chemicals into the fibers, creating adhesion. While this process can be used to meet regulatory requirements, dust can be released during installation, creating a dusty work environment and impeding visibility. The method of the present invention takes the chemically-treated fibers and dries them as individual fibers or matted into desired superstructures. Because the fire retardant is within the fibers, the present invention dramatically reduces the amount of chemical dust produced during installation.

The optional chopper 100 may be used in place of the optional fiberizer 170, but is used prior to drying the treated fibers. In that manner, dust formation is reduced compared to when the fiberizer 170 is used after drying. Use of the chopper 100 breaks up the clumps in a different manner than the post-drying fiberization and separation described. Specifically, because the fibers are wet, they are more flexible and less susceptible to breakage. In addition, the fibers may be combined with one or more binders to form superstructures prior to chopping. The binder may be a chemical additive suitable for bonding fibers together, and a suitable binder may be a starch, adhesive, or other binder. These superstructures may have spaced bonds between fibers and/or fiber particles that establish voids to improve insulating and density characteristics, and such bonds may be formed directly or through the use of an optional binder. Using the 100 chopper instead of the 170 fiberizer may improve the likelihood of maintaining superstructure integrity because the fibers are more flexible and less brittle in a wet or moist state.

The treated and dried fibers may optionally be sent for testing. The fibrous material that is the cellulose insulation of the present invention may be tested for compliance with all standards for blown-in cellulosic fiber insulation as mandated by C-739, HH I515, and the Consumer Product Safety Council. The treated fibers made using the method of the present invention may be used for insulation as a fire retardant, thermal, acoustical, and radiant barrier material.

In addition to being used to separate fibers with different characteristics, the partitioning device 50 may also separate contaminants from the fibers of the feedstock. These contaminants from the recycled feedstock material 10 may include glass, plastic, or other non-cellulosic elements, for example. The partitioning device 50 may be comprised of a screening system or a cyclone separator, which are two examples of partitioning technologies that may be applicable. The partitioning device 50 may additionally include, or instead be, a screening apparatus, such as that shown at: https://www.andritz.com/products-en/group/pulp-and-paper/pulpproduction/kraft-pulp/pulp-drying-finishing/pulp-screening-cleaning, for example, to facilitate sorting of the fibers prior to introducing the feedstock material into the mixer 60.

The optional dry classifier 180 may be used to size separate the treated and dried fibers so that relatively small particles that are effectively dust particles are removed from the product to minimize the inclusion of dust in the finished product. The dry classifier 180 may be a screening apparatus or an air classifier. An air classifier may utilize an upward air flow to separate lighter elements from heavier elements, for example. The dry classifier 180 may operate to separate fibers based on size, density, hydrodynamic diameter, or other characteristics that have been shown to separate high yield product from less desirable fractions of the product.

Examples of the product of the present invention were prepared using the method of the present invention as described herein. Fibers separated by a pulping process, and sorted by a sorting system, were treated with fire-resistant chemicals, blended with other fiber sources, and dried to produce the finished product. The finished product was tested to ASTM C739 and found to be in full compliance. The product was supplied to field installers and was found to be a high-quality, low-dust finished product.

Claims (10)

i. A method for manufacturing a blown-in-place fire retardant insulation, comprising the steps of: introducing into a mixer (60) fibers of one or more raw materials; introducing one or more solvents into the mixer (60); introducing into the mixer (60) one or more fire retardant chemicals (110); mixing the fibers, the one or more solvents and the one or more fire retardant chemicals (110) in the mixer (60) for a time sufficient to retain the one or more fire retardant chemicals (110) on and within the fibers to form treated fibers; and drying the treated fibers to form blown-in-place fire retardant insulation, characterized by partially dehydrating the fibers of the one or more raw materials, before introducing the fibers into the mixer (60); and wet separating partially dehydrated fibers at some point after partially dehydrating the fibers. 2. The method of claim 1, wherein the separating step includes the step of classifying the separated wet fibers (30), prior to introducing the separated fibers into the mixer (60). 3. The method of claim 1, further comprising the step of recovering residual fiber powder (190) from the separated fibers, prior to introducing the separated fibers into the mixer (60). 4. The method of claim 1, further comprising the step of removing residual fiber dust (190) from the separated fibers, prior to introducing the separated fibers into the mixer (60). 5. The method of claim 1, further comprising the step of removing residual fiber dust (190) from the treated fibers after the drying step. 6. The method of claim 1, wherein the feedstock includes one or more feedstocks (10) of recycled material and/or wherein one or more feedstocks include one or more of cereal straw, animal feathers and other lignocellulosic agricultural by-products. 7. The method of claim 1, further comprising the step of adding one or more additives to the mixer (60) before or during the mixing step. 8. The method of claim 1, further comprising the step of classifying the treated fibers, after the drying step. 9. The method of claim 1, further comprising the step of recovering residual fiber dust (190) from the treated fibers after the drying step. 10. The method of claim 1, further comprising the step of combining portions of waste fiber powder (190) to form treated fiber superstructures, particularly wherein the step of combining portions of waste fiber powder includes combining the waste fiber powder (190) with a binder.